Nonaqueous Battery Negative Electrode Noncoated Edge Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in achieving excellent large current properties due to high internal resistance, which deteriorates performance during high-current charge-discharge cycles.
Innovation Solution
The battery design incorporates a positive electrode and negative electrode with specific active material layers and current collectors, featuring noncoated portions adjacent to edges, optimized density, and mass ratios to reduce internal resistance and enhance contact area, allowing for efficient high-current discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the battery is designed for high current discharge, then large current property is improved, but internal resistance increases causing performance deterioration
Solution Approach 1:
The negative electrode is designed with noncoated portions at specific locations (edges) where different functional requirements exist. These noncoated portions reduce local resistance and improve current distribution, while the coated portions maintain capacity. This local differentiation resolves the contradiction by optimizing both large current property and internal resistance simultaneously.
Solution Approach 2:
The negative electrode active material layer is segmented into coated portions and noncoated portions. The noncoated portions are strategically placed at edges to reduce contact resistance and improve electron collection, while the coated portions provide the main capacity. This segmentation allows the electrode to simultaneously achieve low internal resistance and high capacity.
2Reliability
If the noncoated portion length is increased, then contact area is improved reducing internal resistance, but energy density is reduced
Solution Approach 1:
The length of the noncoated portion is precisely controlled within the range of 5-20 mm. This parameter optimization ensures sufficient contact area for low internal resistance while minimizing the loss of active material. The specific length range balances the competing requirements of conductivity and energy density.
Solution Approach 2:
Instead of coating the entire negative electrode, only the essential edge portions are left noncoated (5-20 mm). This partial noncoating provides sufficient electrical contact improvement without excessively reducing the active material quantity. The solution uses just enough noncoated area to achieve the desired effect while preserving energy density.
Data Source
AI summary
According to one embodiment, there is provided a nonaqueous electrolyte secondary battery. A negative electrode current collector comprises a coated portion on which the negative electrode active material layer is provided and a noncoated portion which is adjacent to the coated portion, in which the negative electrode active material layer is not present. A density of the negative electrode active material layer is within a range of 2.1 g/cc to 2.4 g/cc. A ratio W1/W2 of a mass of the coated portion per unit area (W1) to a mass of the noncoated portion per unit area (W2) is from 0.997 to 1.